The present invention relates to a process and an apparatus for preparing active ingredient dispersions.
It is nowadays necessary in many sectors of the chemical industry to prepare active ingredient dispersions, eg. in the color and dye industry and the drugs industry. In this connection it is often impossible to disperse the active ingredient, eg. the dye or the drug, directly in an aqueous liquid. In particular, the active ingredient particles are then not in the desired micronized form.
The preparation of very finely divided, micronized carotenoids in an aqueous dispersion is described in DE-A 29 43 267. In this case, a carotenoid is dissolved in a supercritical gas in an autoclave, and the resulting solution is dispersed in a suitable aqueous colloidal matrix, which is located in a second autoclave, using an agitator. The resulting dispersion consists of droplets of fluid gas containing active ingredient in water. This two-phase system is decompressed, with the gas being continuously discharged from the autoclave, whereas the liquid can be removed only batchwise after completion of the process. This process results in an average particle size of the carotenoid of less than 1 micron. A disadvantage is that phase separation may occur during the decompression process so that the active ingredient is insufficiently stabilized by the liquid matrix. In addition, a loss of active ingredient must be accepted.
European Patent 0 322 687 proposes a process for preparing a drug form comprising an active ingredient and a carrier. This entails a fluid gas, an active ingredient and carrier materials, which can also be dissolved in a liquid, being introduced into a spray tower so that the fluid gas picks up active ingredient and carrier. The fluid gas is subsequently separated from the resulting active ingredient/carrier combination in a separator so that the combination can be removed from the separator. This process produces dry active ingredient particles but not liquid dispersions. Fluid gas means a substance which is in the form of a gas or vapor under atmospheric pressure and which has been compressed to the vicinity of its critical point or beyond and is therefore in the form of a sub- or supercritical fluid.